We propose to study the processes of chemically-induced metagenesis and carcinogenesis using human cells in culture. We specifically propose to characterize our new human cell gene-locus mutation assay by examining the behavior of cell lines derived from additional human donors, of additional gene loci in our MIT-2 line, and of other classes of chemical mutagens and carcinogens not yet examined. We propose to use our human cell mutation assay in studies of mutation caused by multi-generational exposure to low concentrations of mutagens and to use split-dose protocols to discover to which classes of chemical mutagens and carcinogens human cells respond with DNA repair. In the area of drug metabolism, we propose to continue our studies of the post-mitochondrial supernatant as a drug metabolising element, building on our present ability to prepare an active, sterile and nontoxic element compatible with human cell mutations assay with the aim of developing techniques for the routine use of stored preparations of human liver. Furthermore, we propose and request support to continue our studies of in vitro carcinogenesis with the goal of developing a novel, nonsubjective assay for neoplastic transformation using primary human lymphocyte cultures.